Knowledge on Sudden Oak Death (SOD) is evolving. Please
email our web master if you find inaccuracies or believe information
should be added to this page (info@cpoabigsur.org).

Background

SOD has been killing oak trees in the Big Sur Valley for years. Pfeiffer
Big Sur State Park has lost thousands of oaks to the disease and SOD has now
been confirmed at various locations in the Big Sur area from the Palo Corona
Ranch on the north to the San Luis Obispo County line. SOD seems to move
inland up the lower / cooler portions of canyons, then uphill on the forested
/ north slopes of ridges.

If
they are present, Tan oaks are usually first to be affected in an area. Coast
Live Oaks, California Black Oaks, and Shreve's Oaks are also susceptible to being
killed by SOD. Oaks in the white oak group appear to not be affected (e.g.,
Valley Oaks, Blue Oaks).

There are a number of trees and shrubs that host SOD but are not killed by it. For
example, the leaves of Bay Laurel trees may be infected with SOD without killing
the tree. It appears that Bay Laurel aids in the spread of SOD to oaks
by hosting the pathogen on its leaves where spores are produced that then infect
nearby oaks. Madrone is also a host, and it is now suspected that SOD not
only infects the leaves and branches of Madrones but is killing them as well. Toyon
is another known host, as are a growing list of about twenty other plants.

The active pathogen is a fungus, Phytophthora
ramorum. Oak trees are killed
when the fungus encircles their trunk under the bark, effectively girdling the
tree. Some oaks succumb to SOD within a few months after first symptoms
appear and others may live several years before dying. It appears the fungus's
spores are spread by air, water, and contact.

The University of California has a web site with maps showing where SOD has been
reported (http://kellylab.berkeley.edu/SODmonitoring). You
can use the same web site to report the location of confirmed cases of SOD.

Diagnosis

A diagnosis of SOD may be confirmed only by culturing the fungus under controlled
conditions or by DNA analysis. Many of the symptoms described below may
be mimicked by pathogens other than Phythophthora ramorum. However, symptoms
have a high probability of indicating SOD if they occur on trees that are within
several miles of an area confirmed with SOD. Samples to be cultured may
be taken from suspect leaves or from under the bark near a canker on the trunk
of trees. If you suspect SOD in a location where it has not been confirmed
and want to have a sample tested, contact Brad Oliver for instructions on how
to collect and submit a sample (biologist at the Monterey County Agricultural
Commissioners Office in Salinas; (831) 759-7325; oliverb@co.monterey.ca.us). More
contact information may be found on the California
Oak Mortality Task Force contact web page.

The primary SOD symptom on Coast Live Oaks is often (though not always) one or
more visible cankers on their trunk (see figures 2 and 3). The canker is
usually low on the trunk, often close to ground level, and is rarely higher than
eight feet. The canker typically oozes a viscous dark brown liquid and
smells like it is fermenting (smells like a wine cork or a used wine barrel). Before
the canker develops some trees exhibit weeping of dark brown viscous liquid through
healthy-appearing bark. Live Oaks are not known to display symptoms on
their leaves other than a general lack of vigor as the tree declines. The
ultimate indication that SOD may be in an area is a cluster of dead oaks with
no other apparent cause of death.

Initial symptoms on Tan oaks are varied, and may include brown blotches on leaves
and wilting of new-growth shoots (giving the appearance of a shepherd's crook
at the growing tip). While Tan oaks may have a canker similar to Live Oak,
they may also display only a faint brown stain on a portion of their trunk, or
no stain.

Bay
Laurel displays symptoms on its leaves. There is typically a characteristic
black line and yellow halo between a darkened portion of the leaf and healthy
green tissue (figure 4). The darkened part of the leaf is usually oriented
so it is the part of the leaf where water droplets linger after moisture has
collected.

Other pathogens can cause symptoms that look like SOD symptoms. Follow
this link for more complete information
on recognizing SOD symptoms in about 15 different hosts, a paper prepared
by University of California and USDA researchers in July of 2003. The paper
is a 1.7MB pdf file and requires free Adobe Acrobat Reader software to read (a
9MB+ download from Adobe).

Treatment

The treatment generally accepted as effective on SOD is application of potassium
phosphonate (PP), also known as potassium phosphite. Other potential methods
of reducing the likely hood of attack by SOD are being investigated, including
treatment by smoke.

PP seems to act as both a nutrient and a fungicide. PP
is used by trees to strengthen cellular membranes, making them resistant to
the fungus. PP
also seems to be converted by trees into chemicals that are toxic to the fungus. Controlled
tests by University of California researchers have shown that PP can help control
SOD, and PP has been used for many years to treat other strains of Phytophthora that
attack other kinds of trees. It is not yet known how effective PP
will prove to be treating SOD in real-world conditions over time. An Australian
company called Agrichem has obtained a special registration for fungicidal use
of PP so it may be used on oaks to combat SOD.

Agrichem's trade name for the product is Agri-Fos. Agri-Fos may be injected
into or sprayed onto oak-tree trunks. Until recently, injection was the
only method recommended for Tan oaks, but it now appears that spray application
on Tan oaks is also effective, though it takes longer for the PP to penetrate
Tan oak bark than with other oaks. When sprayed on the trunk of oaks Agri-Fos
must be mixed with another Agrichem product called Pentra-Bark to help the Agri-Fos
penetrate through the bark and into the tree's tissues. Once inside the
tree, the tree distributes the chemical through its system. One quart of
Pentra-Bark is enough to mix with about 5 gallons of undiluted Agri-Fos. Agri-Fos
is typically sold in 2 1/2 gallon containers (other sizes are available).

When spraying the trunks of oaks with a mixture of Agri-Fos and Pentra-Bark,
the tree is sprayed from ground level to about 6 to 9 feet above ground level
with enough solution to soak the bark just to run-off. Ensure that cracks
and crevices receive plenty of solution as they are the shortest pathway into
the tree's system, both for the treatment and the pathogen. An ordinary
garden or back-pack sprayer may be used, set for a course droplet size to avoid
excessive spray drift. To avoid waste of Agri-Foss, portions of trunks
with moss that is so heavy as to interfere with spray reaching the tree's bark
may be brushed to remove excessive moss, or if a relatively small area, may be
sprayed around. The spray should not be applied when it is raining, but
rain after application apparently does not affect results. The solution
will likely discolor or kill moss and lichen. Avoid spraying leaves with
solutions containing significant amounts of Pentra-Bark as it will likely injure
or kill leaves it contacts. Ask your supplier for a copy of Agrichem's
spray application directions and follow them.

Injecting trees with Agri-Fos uses the least amount of the fungicide, but is
labor intensive. Small holes are drilled through the bark deep enough to
penetrate into sap-wood and diluted Agri-Fos is immediately injected. Various
devices are available for injecting trees, from inexpensive plastic hypodermic-like
devices to sophisticated drill and injector combination tools with a significant
price tag (e.g., www.treeinjectors.com). There
is disagreement over the desirability of sealing injection holes after use. One
SOD researcher said he has never seen re infection at an unsealed injection hole
site, even when holes receive splash from SOD infected soil. Ask your Agri-Fos
supplier for a copy of Agrichem's injection application directions and follow
them to determine the correct dilution, number of holes, and quantity to inject
per hole.

The manufacturer's recommendation is to apply Agri-Fos twice a year. Agri-Fos
should not be applied when a tree is dormant as the tree will then not effectively
move the chemical through its tissues. Coast Live Oaks are dormant in summer,
generally July to October. Black Oaks are deciduous and are dormant in
winter when they lose their leaves.

Ideally, trees should be treated before they show symptoms so they will be strengthened
by the nutrient properties of PP to resist initial attack by the fungus. Treatment
has a better chance of success if applied within a couple of months of when symptoms
first appear. The time and expense involved in treatment will often mean
choosing between trees you want to try to protect and those you will leave on
their own. A paper has been prepared by University of California researchers
that provides guidelines
for analyzing which trees are most at risk for SOD, and which are most likely
to benefit from treatment (34K pdf file).

Materials

The only local dealer we know of that sells Agri-Fos and Pentra-Bark is HealthySoil in Gonzales in the
Salinas Valley; www.healthysoil.com; tom@healthysoil.com,
831-675-3144 x102. HealthySoil is located at 425 Alta
Street, Building 16, Gonzales. Call before you make the trip to
be sure someone
will be available to help you (sometimes everyone is in the
field). Agri-Fos
and Pentra-Bark are also available from Bioscape in Petaluma,
California; www.bioscape.com;
(877) 246-7227.

Please let us know if you learn of another source for Agri-Fos so we can post
it. Also, please let us know if you have had a good experience hiring an
arborist or other service to treat your trees so we may post their contact info.

Our understanding is that the active ingredients in Agri-Fos and Pentra-Bark
are relatively benign, and the Monterey County Agricultural Commissioner's office
assures us you are not required to have a certificate or license to apply Agri-Fos
so long as you are not doing so for hire. However, some dealers are apparently
confused about requirements and are mistakenly asking for an applicator license. If
you have a problem, have the dealer call the Monterey County Agricultural Commissioner's
office at (831) 647-7629 or 759-7325.

More Information

This web page is intended as a readily accessible summary of more detailed information. Much
more SOD information is available on the Internet and we suggest you search the
Internet to learn more. A good place to start is the web site of University
of California SOD researchers. Another is www.suddenoakdeath.org,
which has links to numerous other sites. Agrichem literature should guide
your use of their products and may be obtained from Agrichem's dealers. Agrichem's
U.S. representative, William Stringfellow, is very helpful and is another source
for information on use of Agrichem's products; toll free (866) 309-8600.